Exhaust gas post treatment device

ABSTRACT

An exhaust gas post-treatment system for purifying exhaust gas from an internal combustion engine, and to a corresponding method. The system includes a particle filter, a device having catalytic oxidation function, and at least one mixing chamber which are combined to form a constructive unit.

FIELD OF THE INVENTION

The present invention relates to an exhaust gas including a particle filter having a catalytic oxidation function and at least one mixing chamber, combined to form a constructive unit, and to a corresponding method for exhaust gas post-treatment.

BACKGROUND INFORMATION

Internal combustion engines, in particular diesel-operated motor vehicles, emit a complex mixture of air pollutants including particles, or fine materials, and gaseous compounds, inter alia nitrogen oxides (NO_(x)), carbon monoxide (CO), and uncombusted hydrocarbons (HC). Due to stricter pollutant emission standards that are now in effect, attempts are being made to regulate the quantity of air pollutants emitted by an internal combustion engine.

In exhaust gas post-treatment systems, in addition to an oxidation catalytic converter and a soot particle filter, a selective catalytic reduction (SCR) is used to meet the strict exhaust gas regulations with regard to the NO_(x) portion in the exhaust gas. A reducing agent injected into the exhaust gas stream, standardly urea or a water/urea solution, decomposes into ammonia, which reacts with the nitrogen oxide contained in the exhaust gas, forming water and nitrogen in the presence of a catalyst.

Coated particle filters having catalytic oxidation function are already known, the catalytic material being contained in the form of a coating or in some other way. Corresponding catalytic converters are suitable for oxidizing uncombusted gaseous and nonvolatile hydrocarbons and carbon monoxide to a large extent into carbon dioxide and water. In addition, a portion of the nitrogen oxides (NO_(x)) that are present can be oxidized at the oxidation catalytic converter into NO₂. The hydrocarbon, deposited in the particle filter in the form of soot particles, can be converted to CO₂ using the nitrogen dioxide. This process is known as “passive regeneration.” An increased portion of NO₂ in the exhaust gas promotes a subsequent reduction of the nitrogen oxides (NO_(x)), compared to a smaller portion.

Patent document WO 1999/039809 relates to a system for selective catalytic reduction (SCR) for treating NO_(x) and combustion exhaust gas containing solid particles, there being provided, in combination and in the following sequence, an oxidation catalytic converter, a fine material filter, a source for the reducing agent, an injection device with a reducing agent, and an SCR catalytic converter. An oxidation catalytic converter that is used, also called DOC (diesel oxidation catalyst), promotes the conversion of HC and CO impurities of the exhaust gas, and at least partly promotes oxidation of the fine material into water and carbon dioxide. In addition, the oxidation catalytic converter supports the oxidation of at least a part of the nitrogen monoxide of the exhaust gas into nitrogen dioxide. A higher portion of NO₂ in the exhaust gas supports the conversion of NO_(x) at an SCR catalytic converter, and causes a passive regeneration of the particle filter, deposited fine material particles being oxidized. Disadvantageous are the large space requirement of the components of the exhaust gas post-treatment system, and in particular the situation of the individual components upstream from the SCR catalytic converter. In addition, the voluminous and long configuration of the installation results in a greater distance from the internal combustion engine and, finally, a lower temperature at the SCR catalytic converter. In particular given dynamic operation, in this way premature dosing of reducing agent is prevented, because the dosing can take place only starting from a particular operating temperature at the SCR catalytic converter. Accordingly, a configuration of oxidation catalytic converter, fine material filter, and SCR catalytic converter represents a large thermic mass that causes heat losses and, due to the large number of components, a significant cost outlay.

Patent document DE 2012 015 840 A1 discusses a post-treatment system for exhaust gas from an internal combustion engine that, in a treatment device, combines a particle filter with an SCR catalytic converter. Such a combination is abbreviated as, inter alia, CDS, SDPF, SCRoF, or the like, an SCR catalytic converter being situated on a particle filter substrate. The CDS catalytic converter performs both a particle trap function and also SCR functions. However, in such a combination a high loading of the filter substrate with an SCR catalyst compound is required, which can cause an unacceptably high pressure loss. In addition, high thermic demands are placed on the catalyst compound in order to withstand the high temperatures of a particle filter regeneration. The described post-treatment system is further supplemented by a second purification catalytic converter, for example realized as a diesel oxidation catalytic converter and/or SCR catalytic converter. In such a system, the required installation space, in particular installation length, has turned out to be a problem. The installation length is determined decisively by the length of a mixing stretch that is necessary in order to mix the injected reducing agent adequately with the exhaust gas. The associated heat losses are high. In addition, such a system does not support the passive regeneration of the filter substrate.

Patent document WO 2012/05672 A1 discusses an exhaust gas train of an internal combustion engine having a decoupling element between a hot exhaust gas line and a cold exhaust gas line for compensating vibrations, and having a nitrogen oxide treatment device. In addition, an injection device is provided for a corresponding reducing agent, and a mixing device is provided for mixing the exhaust gas with the reducing agent, which form a unit that is connected to the coupling element.

SUMMARY OF THE INVENTION

According to the present invention, a post-treatment system is provided for purifying an exhaust gas, containing at least nitrogen oxides and soot particles, from an internal combustion engine, which is characterized in that a particle filter, a device having a catalytic oxidation function, and at least one mixing chamber following the particle filter in the direction of flow of the exhaust gas are combined to form a constructive unit. In addition, a method for exhaust gas post-treatment is provided that uses the post-treatment system.

The particle filter and the device having the catalytic oxidation function can be separated spatially, for example being provided on separate elements, or, in a specific embodiment, can be provided as a particle filter having a catalytic oxidation function.

A particle filter having an oxidation catalyst function is configured to carry out particle trap functions and a conversion of pollutants in the exhaust gas, as well as to enable a regeneration of the particle filter. In general, particle filters have a structure, or a barrier, for example in the form of a honeycomb bearer having a multiplicity of mutually closed channels that are realized such that exhaust gas containing particles flows through porous walls of the bearer, and the particles are deposited in pores.

As structures or bearers for catalytic layers, for example honeycomb-shaped wall flow filters or honeycomb-shaped catalyst bearers, for example made of ceramic, can be used. Metallic bearers are also possible. The structure of the particle filter having catalytic oxidation function must permit in particular, as an essential property, the desired particle filter effect, and must enable a catalytic activity that lends the filter the desired oxidation function. As an essential property of this oxidation function, non-oxidative or partly oxidative hydrocarbons and carbon monoxide contained in the exhaust gas or arising during oxidation of particles with oxygen in the exhaust gas train, for example after a targeted temperature increase in the filter charged with the particles, are oxidized at least partly to form CO₂ and water. As a further essential property, the oxidation function can, in addition to the oxidation reactions named above, optionally also oxidize nitrogen monoxide, at least in a limited temperature range, in order to set a mass ratio that is favorable for subsequent reactions for the nitrogen oxides contained in the exhaust gas.

The particle filter, the device for catalytic oxidation or the particle filter having catalytic oxidation function, and the at least one mixing chamber can be combined with one another by detachable connecting elements to form a constructive unit. In a specific embodiment, the constructive unit is situated in a container, which may be in a cylindrical container, or forms such a container.

In particular, the constructive unit is fashioned in such a way that easy access to the particle filter is possible. Thus, the cylindrical container that accommodates or forms the constructive unit can have connecting parts in the form of end parts that detachably connect the cylindrical container to elements of the post-treatment system, the cylindrical container being accommodated on the exhaust gas train. The end parts can be fastened by a clamping device or by screws. Due to the detachable connection of the cylindrical container to the exhaust gas train, the interior is accessible, so that individual elements accommodated therein are also accessible.

The at least one mixing chamber is fashioned to mix an exhaust gas stream, supplied by the upstream elements of the exhaust gas post-treatment system, with a reducing agent that is injected by an injection device or produced thereby.

The at least one mixing chamber is in particular fashioned to convert liquid reducing agent supplied by the injection device to the gas phase, which agent is used in a subsequent reduction catalytic converter, in particular an SCR catalytic converter. In addition, the at least one mixing chamber is structured so as to mix gas phases and/or gas-liquid phases along a mixing stretch.

In general, the flow path of the exhaust gas in an exhaust gas post-treatment system is limited due to the installation conditions and the low heat losses that are to be sought. According to the present invention, through a structuring of the mixing chamber the exhaust gas flow is given an overall path length that is longer than the overall length of the at least one mixing chamber. The mixing chamber can be an essentially tube-shaped element that conducts the exhaust gas flow and promotes a mixing of the exhaust gas flow and reducing agent. The mixing chamber can have a cylindrical cross-sectional shape or some other suitable cross-sectional shape, for example spherical. In addition, the at least one mixing chamber can have internal mixing devices that are fashioned to mix the exhaust gas flow and the injected reducing agent while flow is taking place through the mixing chamber. Corresponding mixing devices, also designated as structures, can be used, in the form of mixing plates, mixing blades, screens, or other known devices acting as static mixers. Dynamic mixing devices are also conceivable, and here a plurality of mixing devices may be used. In order to achieve a good distribution of the injected reducing agent into the exhaust gas flow, in the interior of the at least one mixing chamber corresponding structures are provided that give the exhaust gas flow for example a rotational impulse, or a swirl or turbulence, achieving a good swirl and thus a good distribution of the reducing agent in the exhaust gas flow. The structures can be fashioned in the form of guide surfaces that form at least one helical path, so that the produced exhaust gas/reducing agent mixture leaves the mixing chamber via an outlet in a spiral flow pattern.

The reducing agent is injected into the exhaust gas flow using an injection device. The reducing agent may be injected at a position; the reducing agent injected for example by an injection nozzle can be distributed uniformly and atomized in the exhaust gas while it is conveyed along a flow path. In particular, for reasons of space the distance between the injection device and a downstream reducing catalytic converter should on the one hand be as small as possible, while on the other hand however sufficient dwell time must be available to ensure a satisfactory distribution and atomization of the reducing agent in the exhaust gas flow. In the case of a downstream reduction catalytic converter of the SCR type, which reduces nitrogen oxides contained in the exhaust gas using reducing agent, for example ammonia, the injection device can be configured for example to inject an aqueous urea solution as a precursor of the reducing agent. In this example, the injection device can be charged with an aqueous urea solution with a specified pressure from a supply tank via a dosing device that is situated outside the mixing chamber. The mixing chamber is fashioned to convert liquid injected reducing agent to the gas phase. In addition, the mixing chamber is suitable for mixing gas flows.

The injection device, for example in the form of injection nozzles, can be situated on a cylindrical container that accommodates the mixing chamber in such a way that the reducing agent is injected into the mixing chamber by the injection device in a radial pattern in the direction of the outer circumference. The at least one injection nozzle can be oriented such that the reducing agent is injected at an adjustable angle relative to a fictive or real point of impingement on the wall of the mixing chamber. Through the injection of the reducing agent into the hot exhaust gas flow, the reducing agent is prepared by the heat of the exhaust gas, which further improves its effectiveness.

A specific embodiment of the exhaust gas post-treatment system according to the present invention includes, following the elements combined to form the constructive unit—in particular a particle filter having catalytic oxidation function and at least one mixing chamber—at least one device, in particular at least one catalytic converter, that is accommodated with the constructive unit in the container or forms such a container. This may be a reduction catalytic converter corresponding to the SCR type, situated downstream from the at least one mixing chamber.

In an advantageous specific embodiment, in addition to or instead of one or more SCR catalytic converters, one or more purifying catalytic converters can be provided, such as a diesel oxidation catalytic converter (DOC catalytic converter) and/or an ammonia oxidation catalytic converter (AMO_(x) catalytic converters). Such oxidation catalytic converters can have a suitable material coated with a catalyzing material or containing in some other way a catalyzing material, whereby chemical reactions can be catalytically excited that modify the composition of the exhaust gas. Through the configuration of one or more catalytic converters downstream from the at least one mixing chamber, an NO_(x) reduction can be further continued and/or completed, achieving an increase in the conversion efficiency of the exhaust gas post-treatment system. In particular, a limitation of the ammonia portion in the treated, emitted exhaust gas can be achieved. A catalytic converter can be present that has a first catalytically active region and, situated downstream from the first catalytically active region, a second catalytically active region differing from the first catalytically active region. Thus, the first catalytically active region can be suitable for an SCR method, and the second catalytically active region, situated downstream, can catalyze a further oxidation function.

In a specific embodiment of the system according to the present invention for purifying exhaust gas, in addition to the devices situated in the constructive unit in a cylindrical container, i.e. a particle filter and a device having catalytic oxidation function, or alternatively a particle filter having catalytic oxidation function and at least one mixing chamber, at least one catalytic converter is accommodated in the constructive unit. In this way, there results an extremely compact exhaust gas post-treatment system which may have only a single container in which a plurality of devices having various functions are combined. For example, the substrate of the at least one catalytic converter can have an upstream region and a downstream region, an SCR catalytic converter being situated at the upstream region and an oxidation catalytic converter being situated at the downstream region.

In a specific embodiment, the constructive unit situated in a cylindrical container includes a particle filter having a catalytic oxidation function, at least one mixing chamber, and an SCR catalytic converter, the cylindrical container having at least one removable end part that is fashioned to ensure access to the interior of the cylindrical container, which may be to the particle filter having the catalytic oxidation function. An exhaust gas stream flowing into the constructive unit from an internal combustion engine is treated in such a way that an NO conversion efficiency is achieved that is at least at times more than 50%, which may be more than 90%, particularly may be more than 95%, and which may be more than 99%. In particular, correspondingly high efficiency values are achieved at advantageous operating points of the internal combustion engine.

In addition, a method is provided for treating an exhaust gas stream that results from an internal combustion engine, the still-untreated exhaust gas having between about 2 g NO_(x)/kWh and 12 g NO_(x)/kWh. The exhaust gas stream is supplied to a system for exhaust gas post-treatment that includes, in a constructive unit, a particle filter having catalytic oxidation function and at least one mixing chamber, pollutants in the exhaust gas stream being catalytically oxidized and particles being filtered out of the exhaust gas stream using the particle filter. A first treated exhaust gas stream produced in this way is supplied to the at least one mixing chamber, in which the first treated exhaust gas stream is mixed with an injected reducing agent to form an exhaust gas/reducing agent mixture.

In a development of the method, the exhaust gas/reducing agent mixture is supplied to a catalytic converter device, a second treated exhaust gas stream exiting from this catalytic converter device being produced. This second treated exhaust gas stream can be catalytically treated in a subsequent oxidation catalytic converter, the ammonia contained in the second treated exhaust gas stream in particular being catalytically converted.

In addition, the method according to the present invention is set up to acquire relevant parameters of the exhaust gas post-treatment system and to evaluate the ascertained data in at least one control unit, sensors and various devices being included in order for example to ascertain particle mass, number of particles, exhaust gas pressure, temperature, exhaust gas flow quantity, reducing agent quantity, exhaust gas composition, exhaust gas concentration, and reduction and/or oxidation potential. In addition, a method is provided for the at least one control unit in order to enable adaptation through modification of a selection of parameters of the internal combustion engine and/or modification of the parameters of the exhaust gas post-treatment system, for example the exhaust gas pressure, the temperature, the exhaust gas flow quantity, the reducing agent quantity, the exhaust gas composition, the exhaust gas concentration, and the reducing and/or oxidation potential, in order to enable a maximally efficient carrying out of the method.

Advantages of the Invention

The solution provided according to the present invention of the exhaust gas post-treatment system creates a constructive unit that achieves reduced installation space and a further reduced overall mass, and thus also a reduced heat capacity of the system. Due to the reduced constructive size of an integrated system according to the present invention, the temperature-dependent response behavior is improved in particular at low temperatures, resulting in an earlier beginning of conversion. This is advantageous in particular in those applications in which internal combustion engines are frequently operated at low temperatures. In addition, the costs of a corresponding exhaust gas post-treatment system can be reduced compared to the previously known systems, which have turned out to be disadvantageous due to the large number of components and their configuration.

Through the design of the constructive unit, accommodated in a cylindrical container, a large number of containers can be omitted that have turned out to be problematic due to their complexity, the overall size of the system, and costs. In addition, additional supporting structures for the complex configuration of the individual elements can be omitted. Due to the compactness provided by the constructive unit, the exhaust gas post-treatment system can be situated in the immediate vicinity of or directly on an internal combustion engine, so that decoupling elements that would otherwise have to be provided can be omitted, or can be more favorably realized.

Through the possibility of placing the compact exhaust gas post-treatment system close to the internal combustion engine, the heat losses are kept low compared to the systems known from the existing art. In particular high temperatures in the mixing chamber integrated in the constructive unit enable an additional dosing of reducing agent into the at least one mixing chamber in the case of dynamic operation of the internal combustion engine, leading in turn to a more effective conversion of the pollutants contained in the exhaust gas stream. In addition, in this way the reducing agent dosed into the hot exhaust gas is further prepared by the heat of the exhaust gas, which further improves the functioning of the exhaust gas post-treatment system according to the present invention.

An advantageous effect is also achieved by the high temperatures for the particle filter having catalytic oxidation function that can be realized through the compactness according to the present invention; thus, for example the reaction speed of the oxygen and/or of the nitrogen dioxide with the deposited soot particles and the pollutants present is greater. The introduction and controlling of a possible thermal regeneration of the particle filter having catalytic oxidation function also turns out to be less demanding and thus able to be realized with lower outlay.

In addition, the integration of further catalytically active elements can improve the conversion of components present in the exhaust gas stream. In this way, for example greater throughputs can be achieved in devices situated downstream through the oxidation of nitrogen monoxide. In addition, an oxidizing effect of the filter functionalized in this way relative to hydrocarbons, upstream from another catalytic converter whose functioning is negatively influenced by hydrocarbons, can protect this latter catalytic converter.

An integration of an additional ammonia oxidation catalytic converter in the configuration of the catalytic converters enables an oxidation of excess ammonia not required as reducing agent, reducing the environmental damage and risk of corrosion due to this gas.

With the sensors provided according to the present invention, for example a gas sensor and/or a temperature sensor, there is the possibility of an improved controlling of the conversion of the pollutants present in the exhaust gas. For example in a controlling of the conversion of nitrogen oxides, the quantity of reducing agents can be influenced in order to obtain an optimal conversion, and on the other hand the temperature can be regulated in order to remain in an optimal window for the course of the catalytic activity.

Through one or more detachable connections at least of a part of the cylindrical container, access to the individual elements is ensured, which elements can be removed and cleaned or exchanged.

Further advantages and specific embodiments of the subject matter of the present invention are illustrated by the drawings and are explained in more detail in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an internal combustion engine having an exhaust gas post-treatment system according to the present invention.

FIG. 2 shows a perspective view of a mixing chamber.

FIG. 3 shows a top view of the mixing chamber according to FIG. 2.

FIG. 4 shows a view of a constructive unit of the exhaust gas post-treatment system according to the present invention.

FIG. 5 shows a cross-section through an exemplary embodiment of an exhaust gas post-treatment system according to the present invention.

DETAILED DESCRIPTION

In FIG. 1, reference character 10 designates an internal combustion engine that is controlled by a (schematically shown) control unit 12 via signal lines. Exhaust gas is conducted away via an exhaust gas train 14 along a flow path 15 in which there is situated an exhaust gas post-treatment system 16. Exhaust gas post-treatment system 16 includes a particle filter 17 (shown only schematically in FIG. 1) and a device having catalytic oxidation function 19, which, combined, can form a particle filter having catalytic oxidation function 18.

In addition, at least one mixing chamber 20 is shown, combined with the particle filter having catalytic oxidation function 18 to form a constructive unit 22. With the particle filter having catalytic oxidation function 18, on the one hand particles are filtered out from the exhaust gas flowing in exhaust gas train 14, and a catalytic oxidation function is induced at the catalytic converter integrated in the particle filter having catalytic oxidation function 18.

The particle filters having catalytic oxidation function 18 have for example a honeycomb structure having a large number of channels that are mutually sealed in such a way that the particle-charged exhaust gas flows through porous walls of the honeycomb body, the particles, formed essentially by carbon, being deposited in pores of the walls. The particle filter having catalytic oxidation function 18 can have a corresponding coating of the channels of the honeycomb body, or can be made up of a catalytically active mass. A regeneration of the particle filter having catalytic oxidation function 18 can be realized in such a way that a conversion, induced by the oxidation catalytic converter, of nitrogen monoxide from the engine exhaust gas with oxygen takes place in catalyzed fashion to form nitrogen dioxide, and the carbon present as soot particles deposited in the particle filter having catalytic function 18 is oxidized with the nitrogen dioxide. Both nitrogen dioxide and nitrogen monoxide are carried out from the particle filter having catalytic oxidation function 18, and are supplied to the further post-treatment. In the case of oxidation of deposited soot particles with oxygen, particle filter 18, provided with the catalytic oxidation function, is capable of oxidizing incompletely combusted intermediate products, for example carbon monoxide.

In FIG. 1, further downstream from the particle filter having catalytic oxidation function 18 a mixing chamber 20 is indicated; these are combined to form a constructive unit 22. Constructive unit 22 is made such that exhaust gas that flows through constructive unit 22 comes into contact with the catalytic centers of the particle filter having catalytic oxidation function 18 and is then conducted to mixing chamber 20. In particular, constructive unit 22 is fashioned as a cylindrical container 44 in which the particle filter having catalytic oxidation function 18 and mixing chamber 20 are combined.

An injection device 24 is situated on constructive unit 22 in such a way that a reducing agent is injected into the exhaust gas stream and is mixed therewith to form an exhaust gas/reducing agent mixture. For example, injection device 24 can include one or more injection nozzles 36 that are fashioned to inject reducing agent into the exhaust gas stream and in particular into mixing chamber 20. For example, injection nozzles 36 can be situated radially on the circumference of constructive unit 22. Injection device 24 can include, in addition to injection nozzles 36, a fluid source and a control unit, which are not shown in FIG. 1. The reducing agent can for example be gaseous ammonia, ammonia in aqueous solution, aqueous urea, or any other reducing agent known in exhaust gas technology.

Mixing chamber 20 is fashioned to improve a mixture of the injected reducing agent with the exhaust gas stream in mixing chamber 20. Thus, mixing chamber 20 can have structures 26 that form a rotational flow inside mixing chamber 20. FIG. 2 shows a specific embodiment of a mixing chamber 20 in a perspective view. Exhaust gas flowing along flow path 15 first moves into the particle filter having catalytic oxidation function 18, and enters downstream into mixing chamber 20. In mixing chamber 20, in FIG. 2 structures 26 are indicated that deflect flow path 15 of the exhaust gas in such a way that this gas assumes a radial orientation relative to a main direction of flow 28. For this purpose, structures 26 can include guide surfaces 30 fashioned for example in the form of a helical path. Optionally, guide surfaces 30 are fashioned on one or more linings 31 accommodated in mixing chamber 20, a spiral flow pattern 32 being imparted to the exhaust gas in the direction of outlet 34 from mixing chamber 20. Main direction of flow 28 of the entering exhaust gas is blocked by structures 26 accommodated in mixing chamber 20 in such a way that the exhaust gas is guided along guide surfaces 30 in a spiral flow pattern 32 (FIG. 3) and exits from mixing chamber 20 through outlet 34, the outlet direction being oriented essentially parallel to main direction of flow 28. Through structures 26, the path length of flow path 15 of the exhaust gas is increased relative to an overall length of mixing chamber 20.

FIG. 3 shows a top view of mixing chamber 20, structures 26 being indicated fashioned as guide surfaces 30. The exhaust gas entering into mixing chamber 20 is guided by guide surfaces 30 into spiral flow 32, which guides the exhaust gas along a spiral path in the direction of outlet 34 from mixing chamber 20. In addition, injection device 24 for the reducing agent is shown schematically, situated on the circumference of mixing chamber 20 in such a way that reducing agent is injected into the interior of mixing chamber 20 and thus into spiral flow 32 of the exhaust gas stream. Injection device 24 includes one or more injection nozzles 36 that are oriented such that reducing agent is injected into mixing chamber 20 with an adjustable injection angle 38, taking into account the spiral flow 32 of the exhaust gas. Here, injection angle 38 can have different angles relative to a tangent applied at a point 40 of impingement on circumference 42 of mixing chamber 20.

Reducing agent injected by injection nozzle 36 in this way via injection device 24 mixes with the exhaust gas, and is mixed with the exhaust gas while flowing through mixing chamber 20 to form an exhaust gas/reducing agent mixture. In addition, through the heat and vapor of the exhaust gas, an aqueous urea solution used as a reducing agent is hydrolyzed, so that ammonia is formed.

FIG. 4 shows a view of constructive unit 22 in which according to the present invention the particle filter having catalytic oxidation function 18 and mixing chamber 20 are combined to form a constructive unit 22. According to FIG. 4, constructive unit 22 is fashioned as a cylindrical container 44, this container being screwed or locked to exhaust gas train 14 by end parts 46, 47, fashioned for example having flange connections. Thus, the interior of cylindrical container 44, or the elements accommodated therein, i.e. the particle filter having catalytic oxidation function 18 or the mixing chamber 20, are accessible for inspection and/or in order to replace the various elements. Constructive unit 22 can also be connected to the exhaust gas train using coupling elements, conceivably one or more clamps, clips, flexible tube pieces, and/or similar devices, in order to enable a removable connection between cylindrical container 44 and other components. FIG. 4 further shows that one or more catalytic converter devices 48 of exhaust gas post-treatment system 16 can be accommodated in constructive unit 22. Corresponding catalytic converter devices 48 are in particular one or more SCR catalytic converters 50 that are situated downstream from mixing chamber 20 and that act as purifying catalytic converters. The reducing agent mixed with the exhaust gas in mixing chamber 20 is used to reduce nitrogen oxides in SCR catalytic converter 50.

FIG. 5 shows a cross-section of an exemplary embodiment of an exhaust gas post-treatment system 16 according to the present invention. Reference character 15 indicates the flow path of the exhaust gas in exhaust gas train 14, which enters into constructive unit 22 as untreated exhaust gas and, along flow path 15, passes through the particle filter having catalytic oxidation function 18, mixing chamber 20, and downstream catalytic converter device 48, which may be SCR catalytic converter 50. Injection device 24 is situated in the region of mixing chamber 20. In further specific embodiments (not shown) of exhaust gas post-treatment system 16, catalytic converter device 48 can include a plurality of further identical or different purifying catalytic converters, such as an SCR catalytic converter 50, a diesel oxidation catalytic converter (not shown), an ammonia oxidation catalytic converter (not shown). In addition (also not shown), exhaust gas post-treatment system 16 can have one or more probes and/or sensors that are configured to monitor operating characteristics and/or other parameters of exhaust gas post-treatment system 16. 

1-15. (canceled)
 16. An exhaust gas post-treatment system for purifying an exhaust gas of an internal combustion engine, comprising: a particle filter, a device having catalytic oxidation function, and at least one mixing chamber which are combined to form a constructive unit; wherein (i) the particle filter, the device having the catalytic oxidation function or (ii) the particle filter having the catalytic oxidation function and the at least one mixing chamber, are combined with one another to form the constructive unit, which is situated in a cylindrical container or forms such a container.
 17. The exhaust gas post-treatment system of claim 16, wherein the particle filter and the device having catalytic oxidation function are combined to form a particle filter having a catalytic oxidation function.
 18. The exhaust gas post-treatment system of claim 16, wherein the cylindrical container has end parts that detachably connect the cylindrical container to elements of the exhaust gas post-treatment system.
 19. The exhaust gas post-treatment system of claim 16, wherein the at least one mixing chamber has structures and is configured to mix a supplied exhaust gas stream with a reducing agent to form an exhaust gas/reducing agent mixture that is injected by an injection device or is produced by this device.
 20. The exhaust gas post-treatment system of claim 19, wherein the structures of the at least one mixing chamber include guide surfaces that conduct the exhaust gas/reducing agent mixture in a spiral flow pattern to an outlet of the mixing chamber.
 21. The exhaust gas post-treatment system of claim 16, wherein downstream from the at least one mixing chamber there is situated at least one catalytic converter device including at least one SCR catalytic converter, ammonia oxidation catalytic converter, and/or diesel oxidation catalytic converter.
 22. The exhaust gas post-treatment system of claim 21, wherein the at least one catalytic converter device is accommodated with the constructive unit in the cylindrical container or forms such a container.
 23. An exhaust gas post-treatment system for purifying an exhaust gas from an internal combustion engine, comprising: an exhaust gas post-treatment device including a particle filter having a catalytic oxidation function, at least one mixing chamber, and an SCR catalytic converter, which are situated in combined form in a cylindrical container, the exhaust gas post-treatment device converting nitrogen oxides of the exhaust gas resulting from the internal combustion engine at least at times with an efficiency of greater than 50%; wherein the particle filter having the catalytic oxidation function, the at least one mixing chamber, and the SCR catalytic converter are combined detachably with one another, and wherein the cylindrical container has at least one removable end part configured to afford access to the particle filter having the catalytic oxidation function.
 24. The exhaust gas post-treatment system of claim 23, further comprising: an additional catalytic converter device for limiting the ammonia content in the exhaust gas stream exiting from the exhaust gas post-treatment system.
 25. A method for purifying exhaust gas, the method comprising: producing, by an internal combustion engine, an exhaust gas having between 2 g NO_(x)/kWh and 12 g NO_(x)/kWh; conducting the exhaust gas from the internal combustion engine to an exhaust gas post-treatment system, including a particle filter having a catalytic oxidation function and at least one mixing chamber; providing catalytic oxidation of pollutants and deposition of particles from the exhaust gas using the particle filter having a catalytic oxidation function, and producing a first treated exhaust gas; and mixing the first treated exhaust gas with a reducing agent in the at least one mixing chamber to form an exhaust gas/reducing agent mixture; wherein the exhaust gas post-treatment system for purifying an exhaust gas of an internal combustion engine, includes the particle filter having the catalytic oxidation function and the at least one mixing chamber which are combined to form a constructive unit, wherein (i) the particle filter, the device having the catalytic oxidation function or (ii) the particle filter having the catalytic oxidation function and the at least one mixing chamber, are combined with one another to form the constructive unit, which is situated in a cylindrical container or forms such a container.
 26. The method of claim 25, wherein the exhaust gas/reducing agent mixture is further prepared in a catalytic converter device situated downstream from the at least one mixing chamber, and wherein the catalytic converter device produces a second treated exhaust gas.
 27. The method of claim 25, wherein the method is controlled by at least one control unit as a function of a selection of ascertained and evaluated parameters of the exhaust gas post-treatment system, the parameters including at least one of a particle mass, a particle number, an exhaust gas pressure, a temperature, an exhaust gas flow quantity, a reducing agent quantity, an exhaust gas composition, an exhaust gas concentration, a reducing potential, and an oxidation potential.
 28. The method of claim 27, wherein the at least one control unit enables, by modifications of parameters of the internal combustion engine and/or modifications of the parameters of the exhaust gas post-treatment system, a timely adaptation efficiently purify the exhaust gas.
 29. The exhaust gas post-treatment system of claim 23, wherein the efficiency is greater than 90%.
 30. The exhaust gas post-treatment system of claim 23, wherein the efficiency is greater than 95%.
 31. The exhaust gas post-treatment system of claim 23, wherein the efficiency is greater than 99%. 